1. Field of the Invention
The present invention is in the field of sterile packaging for medical apparatus, and method for making such packaging. More particularly, the present invention relates to so called double-sterile packaging for medical apparatus. With this packaging, a newly manufactured non-sterile medical apparatus, such as a cardiac catheter, is first enclosed in an inner first container sufficient to isolate the apparatus from microorganisms in the environment. This inner first container is itself packaged in an outer second container which is also sufficient to isolate the inner first container and apparatus from microorganisms in the environment. The first and second containers each include cooperative areas of a micro-porous sheet material which will freely pass gas molecules, but which will not pass microorganisms from the environment into the containers.
These nested containers are processed in a chamber to remove air from within the containers via the micro-porous sheet material, and to replace the air with a sterilizing gas, such as ethylene oxide. After an interval of time sufficient to insure that all microorganisms inside both the inner and outer containers have been killed, the sterilizing gas is removed and replaced with an inert gas. Subsequently, the packaged medical apparatus is shipped to a site of future use, and may be stored in its double-sterile package on a shelf open to the ambient air, for example, without further need for protection from microbes until the time of its use arrives. When the time arrives to use the packaged apparatus, it may be removed from the double-sterile package and used for human treatment without any need for further sterilization immediately prior to this time of use.
2. Discussion of the Related Technology
Conventional packaging for medical apparatus includes single-sterile packages, one embodiment of which is the familiar envelope found on adhesive bandages, such as on a Band-aid. Another embodiment of such single-sterile packaging takes the form of essentially a plastic bag made of a heat-sealable plastic sheet material. A medical apparatus may be placed into such a bag and the opening of the bag is then heat sealed shut. In order to allow sterilization of the packaged medical apparatus, the bag includes a hole in at least one wall. This hole is spanned and closed by a patch of gas-permeable material which will pass sterilizing gas but not microorganisms. As described above, the packaged medical apparatus is sterilized by use of a processing chamber and a sterilizing gas, such as ethylene oxide.
In such single-sterile packages, the gas-permeable patch may be made of a spun polyolefin sheet material. This material has an appearance, consistency, and feel generally like heavy bond paper, but is considerably stronger than an equivalent weight of paper because it is spun or matted of polyolefin fibers rather than from cellulose (wood fibers) or from other organic fibers (such as rag or cotton). An example of such sheet polyolefin material is available commercially under the trade name of TYVEK from Dupont Company. This TYVEK sheet material is micro-porous so that a sterilizing gas may pass readily therethrough. However, TYVEK sheet material will not pass microorganisms from one side to the other because the porosities of the material are simply too small. In order to secure the patch of TYVEK material to the wall of the heat-sealable bag, a peripheral annular part of the patch is heat sealed to the sheet plastic material from which the bag wall is formed. In this case, because the bag is polyethylene sheet material and the TYVEK patch is essentially polyethylene material, these two materials are essentially common to one anther, and can be heat sealed together.
Such single-sterile packaging bags are generally used for storing medical devices which are not of a critical nature. However, for storing critical medical devices (such as cardiac catheters and other apparatus which are either to be used with critical patients, or which are to be introduced deeply into the human body, or both), so that the risk of serious and possibly fatal infection from a lack of absolute sterility is great, then a higher level of protection for the sterility of the apparatus is required of the packaging used for this apparatus. For these critical-use medical apparatus, a double-sterile package technology has been developed.
A conventional double-sterile package for a cardiac catheter includes an inner first container having a tray-like member formed of substantially rigid and shape-retaining plastic sheet material. This tray-like member defines a recess or recesses into which the components of the cardiac catheter are received, and also defines an upper out-turned planar peripheral flange which completely circumscribes and defines an opening to the recess of the tray-like member. In order to close this opening defined within the peripheral flange, a single continuous flat closure sheet of micro-porous material spans across and closes this opening. This closure sheet may be made of TYVEK sheet material, for example. The closure sheet of micro-porous material rests upon and heat-seal bonds to the out-turned flange of the tray-like member continuously around the periphery of the recess in this member.
A heat-seal bond is defined between the flange feature of the tray-like member and the flat closure sheet of micro-porous material. This sheet of micro-porous material alone would not heat seal bond to the plastic material from which the tray-like member is formed. In order to effect this heat-seal bond, the sheet of micro-porous material carries on its inner face a dispersed or discontinuous layer of heat-bonding material. This layer of heat-bonding material must be dispersed or discontinuous in order to preserve some of the porosity of the micro-porous sheet material. This heat-bonding material is effective upon the application of localized pressure and elevated temperature, as in a heat-sealing machine, to effect the necessary heat-seal bond between the closure sheet and tray-like member. This heat-seal bond is circumferentially continuous and is impervious to microorganisms in the environment, but may be peeled open by manual force.
The inner first container is received into an outer second container, which is essentially a partially transparent plastic bag. The outer second container has a pair of generally unequally-sized rectangular flat opposed walls, one made entirely of flexible transparent plastic sheet material, and the other being made partly of flat transparent plastic sheet material, and partly of flat micro-porous sheet material. These two flat walls are heat sealed to one another along three edges to form a rectangular bag with one open edge. The one wall of flexible plastic sheet material extends beyond the portion of the opposite wall which is formed by such plastic sheet material. This extension of the longer wall is confronted by a closure flap portion of the opposite wall which is formed by the micro-porous sheet material. This closure flap portion is also coated on its inner face with heat-bond material, as is described above.
In the manufacture of this outer container bag, the shorter wall is formed with the closure flap heat sealed along one edge of the shorter wall leaving an extending free-flap part of the closure flap overlying the shorter wall. This free-flap portion provides for later manual grasping of the flap so that the outer container bag can be peeled open. The closure flap is sized so that it makes up the difference in size between the two walls of plastic sheet material, and is congruent at its marginal edge with the marginal edge of the longer wall. Thus, the longer wall of plastic sheet material and the closure flap of micro-porous sheet material leave an open edge to the bag through which the inner container may be inserted. After the inner container is inserted into the outer container bag, the open edge of the outer container bag is heat sealed closed. That is, the longer wall of plastic sheet material and the closure flap of micro-porous sheet material are heat-seal bonded to one another at their congruent marginal edge portions. A continuous heat-seal closure is thus formed for the outer container bag. This double-sterile package is then inserted into a handling and storage box. Although this box is primarily for handling and storage purposes, it additionally provides a convenient space upon which important information about the medical apparatus can be printed in a number of languages. A number of such boxed and packaged medical apparatus are sterilized simultaneously using a sterilizing gas, as is described.
More particularly, the contents of this conventional double-sterile package within its handling and storage box are sterilized in the conventional way using a sterilizing gas, such as ethylene oxide. Adequate ventilation of the sterilizing gas both into and out of the recesses of the inner first container, and to and from the surfaces of the cardiac catheter therein, is provided because the closure flap of the outer container bag overlays a portion of the closure sheet of the inner container. Some additional ventilation of the inner first container may be achieved via the remainder of the micro-porous closure sheet, even though this remainder portion is overlaid or covered by the impermeable plastic sheet material of the outer container bag.
With a conventional double-sterile package for medical apparatus as described above, the micro-porous closure sheet of the inner first container and the micro-porous sheet material closure flap of the outer container bag each carry a dispersed or discontinuous layer of heat-sealing material on their inner surfaces. This layer of heat-sealing material reduces the permeability of the micro-porous sheet material by a factor of about 10. That is, the permeability of the micro-porous sheet material is reduced from its value of about 20 seconds per 100 cc per square inch (hereinafter sec/100 cc/sq.in.) in its un-coated state to about 150-200 sec/100 cc/sq.in., with the layer of heat-sealing material. As a result, in order to achieve adequate ventilation of the sterilizing gas to and from the surfaces of the packaged medical apparatus, a considerable area of the micro-porous sheet material must be used in each conventional double-sterile package. This ventilation rate for a package is a function of contained volume within the package and the permeability of the micro-porous sheet material. If this ventilation rate is not maintained for a particular package design, then the time required for the sterilizing operation is considerably increased, adding significantly to the costs of the medical apparatus as delivered to a patient. However, the micro-porous sheet material is itself very expensive, and the relatively large amount of this material used in each conventional double-sterile package for a medical device adds significantly to the costs of these devices.
Additionally, the conventional double-sterile package as described above has a number of deficiencies. Because of the nature of the outer container bag, this bag has only a limited amount of space upon which important information about the medical device and its use can be printed. This limited space is defined substantially only on the closure flap of micro-porous sheet material. This closure flap conventionally represents only about one-third or less of the area of one side of the outer container bag. This important information about the medical apparatus must additionally be provided in a number of languages because of the international use of many medical apparatus. Consequently, this lack of available informational space on the outer surfaces of the outer container bag of a conventional double-sterile package is another reason for use of the outer handling and storage box. The important information about the medical apparatus is printed on the outer surface of the box. However, because the handling and storage box is frequently opened first and discarded, while preparations are under way for use of the medical apparatus, information which is set out on the box must be repeated on the double-sterile package itself. As a result, the surface of both the closure flap of the outer container bag, and of the closure sheet of the inner container (which is visible even while the outer container bag is closed because this bag is formed mostly of transparent plastic sheet material) are additionally printed with this important information. Thus, the conventional packaging requires duplicated printing operations because the box is frequently thrown away at an early time.
Further to the above, when a medical apparatus in a conventional boxed double-sterile package is to be used, the medical personnel must first open the box and remove the double-sterile package. The outer container bag of the double sterile package is opened next by peeling open the closure flap of the outer container bag. This allows removal of the inner container from the outer container bag. The inner first container is then opened as a third step by peeling open the closure sheet from the tray-like member. Thus, a three-step opening procedure is required under conditions which are frequently rushed and exigent. Additionally, all of the packaging material for the medical apparatus, including the outer handling and storage box, must ordinarily be treated as contaminated biological waste, which requires expensive special protective disposal procedures.
Further the conventional double-sterile package includes an outer bag-like container, as has been described. This outer container bag is generally rectangular in plan shape. Because the inner container is not necessarily rectangular in plan shape, the two containers define therebetween corner areas outside of the inner container but within the outer container. These corner area define interstitial pocketed or stagnant volumes within which sterilizing gas may accumulate during the sterilizing process, and from which this gas must be purged before the process is considered complete. These interstitial pocketed volumes are not necessary because no part of the packaged medical apparatus is contained outside of the inner container. However, the inner surface of the outer package and the outer surface of the inner package must both be sterile. Thus, there is a real need to ventilate sterilizing gas to and from these pocketed volumes. Because the common sterilizing gasses, such as ethylene oxide, are known or suspected to be powerful carcinogens, considerations of long term exposure for medical personnel who are involved in opening such packages prior to use of the medical apparatus therein dictates that all sterilizing gas be purged from the package. Consequently, such double-sterile packages which define stagnant volumes or pockets such as at the corners of the conventional outer container bag, may require longer sterilizing and purging processes than would otherwise be necessary. Minimizing these stagnant volumes between the inner and outer package is important because their presence increases gas sterilizing processing times and decreases package throughput at the sterilizing facility. Thus, such longer processing times for the sterilizing process significantly increases the cost for the medical apparatus.